1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, a process cartridge and an electrophotographic apparatus. More particularly, it relates to an electrophotographic photosensitive member making use of a support comprising aluminum and having been surface-roughened, a process cartridge, and an electrophotographic apparatus which have such an electrophotographic photosensitive member.
2. Related Background Art
Electrophotographic apparatus can enjoy high speed and high print quality, and are utilized in the field of copying machines and laser beam printers. As electrophotographic photosensitive members used in such electrophotographic apparatus, organic electrophotographic photosensitive members making use of organic photoconductive materials have been brought forth and have come into wide use. Also, with respect to construction, electrophotographic photosensitive members have been changed over from electrophotographic photosensitive members of an electric-charge movement type complex structure or of a single-layer type, in which a charge-generating material has been dispersed in a binder resin, to electrophotographic photosensitive members of a function-separated type in which a charge generation layer and a charge transport layer are functionally separated, and their performances have been improved. The latter function-separated type electrophotographic photosensitive members are so constructed that a subbing layer is formed on an aluminum support and then the charge generation layer and the charge transport layer are formed thereon. Such construction constitutes the prevailing construction today.
With progress in the development of the electrophotographic apparatus, electrophotographic photosensitive members have also been required to provide images having a higher quality level. With regard to improvements in repeating stability and environmental stability of electrophotographic photosensitive members, the charge generation layer, the charge transport layer, and the subbing layer all have an important influence on electrophotographic performance with regard to sensitivity, image quality, and repeating stability. Moreover, as the support, various types, such as extruded tubes, ED tubes (drawn tubes) and EI tubes, have come into use for the purpose of reducing production cost and better preventing faulty images.
However, if the charge generation layer is superposed on the support as it is, any laser light reflects from the support to cause interference fringes. In order to prevent this, it is necessary for the support surface to be roughened by some means. Depending on its shape, the roughened surface is required to have a roughness of about 0.6 xcexcm or smaller as a 10-point average roughness (Rz).
Methods for surface roughening include centerless grinding and honing. The honing method includes dry honing and wet honing, either of which may be used. The wet (liquid) honing method is a method in which a powdery abrasive (abrasive grains) is suspended in a liquid such as water and the suspension formed is sprayed on the surface of a support at a high rate to roughen its surface. The surface roughness can be controlled by the pressure or rate of spraying and the quantity, type, shape, size, hardness, specific gravity or suspension concentration of the abrasive. Similarly, the drying honing method is a method in which an abrasive is sprayed on the surface of a support at a high rate by the aid of air to roughen its surface, and the surface roughness can be controlled in the same manner as in the wet honing method. The abrasive used in these wet honing and dry honing methods may include particles such as silicon carbide particles, alumina particles, zirconia particles, stainless steel particles, iron particles, glass beads and plastic shots.
However, in such dry honing (blasting) and in liquid honing making use of shapeless alumina abrasive grains, abrasive grains may stick in the support surface, appearing as black dots in white images in a reversal development system or blank areas in black images in a regular development system when an electrophotographic photosensitive member is produced using such a support. In liquid honing making use of glass beads, glass may easily break to stick in the support surface to make it difficult to control surface roughness. Accordingly, it is common to roughen the support surfaces by liquid honing using spherical alumina abrasive grains or spherical stainless steel abrasive grains as the abrasive, and thereafter to form thereon the subbing layer, the charge generation layer and so forth to produce electrophotographic photosensitive members.
In a charge generation layer formed of a binder resin in which a charge-generating material pigment has been dispersed, in general, a sufficient sensitivity is easy to attain when the proportion of the pigment is larger. Also, since in recent years there has been an increasing demand for electrophotographic apparatus to achieve higher speed and higher image quality, such a larger proportion of the pigment is used because it is more effective for improving performance. If, on the other hand, the pigment is in a small proportion, the charge generation layer may cause a positive or negative ghost to appear, depending on the electrophotographic processes. In such a case, too, it has been effective to use the pigment in a large proportion. However, with an increase in pigment proportion, the charge generation layer that is formed may have poor film properties and also tends to be affected by the surface shape of the support. Also, in the charge generation layer having such a large pigment proportion, poor film properties may result with an increase in the surface roughness of the support, tending to cause faulty images.
The charge transport layer may wear when formed as a surface layer of the electrophotographic photosensitive member. Accordingly, with respect to the useful life of the member, it is commonly more effective for the layer to have a larger thickness. However, with an increase in layer thickness, the reproducibility of electrostatic latent images may be reduced, and, in the case of digital machines, poor reproducibility of individual dots of exposure spots may result. In digital machines which aim for higher precision, it is difficult to accomplish the requisite image quality and life thereof. Also, where the charge transport layer is formed in a thin film for the purpose of achieving a higher image quality, the surface roughness and the layer thickness may correlate to cause black dots or blank areas, and hence it is more difficult to accomplish both.
The present invention was made taking account of the above problems. Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member in which any interference fringes do not appear at the time of image formation and which does not cause any faulty images, such as black dots, blank areas, and ghosts, and to provide a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.
More specifically, the present invention provides an electrophotographic photosensitive member comprising a support, and a charge generation layer and a charge transport layer provided on the support in this order, wherein the charge generation layer contains a charge-generating material in an amount of more than 2 parts by weight and not more than 5 parts by weight based on 1 part by weight of a binder resin, and the support has a surface roughness in which a maximum height (RmaxD), a 10-point average roughness (Rz), an arithmetic-mean roughness (Ra) and an unevenness average distance (Sm) fulfill the following conditions:
1.2 xcexcmxe2x89xa6RmaxDxe2x89xa65.0 xcexcm,
1.2 xcexcmxe2x89xa6Rzxe2x89xa63.0 xcexcm,
0.15 xcexcmxe2x89xa6Raxe2x89xa60.5 xcexcm,
30 xcexcm less than Smxe2x89xa680 xcexcm.
The present invention also provides a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.